Up to now, energies are emitted, after being used in factories and power plants, in transportation vehicles like automobiles, and also in information processing devices like computers, into the environment in the form of waste heat. Thus, thermoelectric conversion devices capable of recovering and converting such waste heat again to energy attract attention.
A thermoelectric conversion device of the type that uses Seebeck effect is capable of recovering waste heat from various systems and converting the same into electric power while not needing working fluids or complex driving mechanisms, in contrast to conventional thermoelectric conversion systems.
Particularly, strontium titanate (SrTiO3), which has been studied conventionally for application to ferroelectric devices, is free from rare and toxic materials such as tellurium, bismuth, and the like, used in conventional thermoelectric conversion devices and at the same time is capable of realizing a large Seebeck coefficient S that reaches as much as 0.8 mVK−1 at 300K. Further, strontium titanate is capable of attaining a relatively large power factor PF, defined as S2σ (PF=S2σ), of 30-40 μW/cm·K2. Thus, strontium titanate is a promising material for thermoelectric conversion devices. Here σ stands for electrical conductivity of the thermoelectric conversion device. The power factor PF can also be represented as S2qnμ (PF=S2σ=S2qnμ), wherein n stands for carrier concentration per unit volume, q stands for carrier electric charge and μ stands for carrier mobility.